1. Field of the Invention
The present invention relates to an image display apparatus.
2. Related Background Art
In recent years, as the image information amount of a personal computer increases, the display monitor has a higher resolution and a larger number of gradation levels, and processes various composite information such as TV information. With the advent of monitors such as a liquid crystal display and a plasma display other than a CRT, image information is often digitized and processed.
FIG. 13 is a block diagram showing an image display apparatus using a liquid crystal panel as an image display unit.
Referring to FIG. 13, the image display apparatus comprises an input terminal 1 for an analog video signal, an A/D converter 2, an image processing unit 3 for processing a digital image and converting it to a signal suitable for the liquid crystal panel, a D/A converter 4, an image memory 5 used to process an image by the image processing unit 3, an input terminal 6 for a video signal synchronizing signal, and a drive pulse generator 7 for generating various drive and control pulses from the synchronizing signal. Pulses from the drive pulse generator 7 serve as control pulses for the A/D converter 2, D/A converter 4, and image processing unit 3, and a drive pulse for an image display unit 8. The analog signal converted by the D/A converter 4 serves as an image input signal for the image display unit 8.
FIG. 14 is a circuit diagram showing the arrangement of the liquid crystal panel as an example of the image display unit 8. Referring to FIG. 14, a shift register (HSR) 9 functions as a horizontal scanning circuit and receives a start pulse (xcfx86HST) 10 and a horizontal shift clock (xcfx86HCK) 11. A shift register (VSR) 12 functions as a vertical scanning circuit and receives a start pulse (xcfx86VST) 13 and a vertical shift clock (xcfx86VCK) 14. The liquid crystal panel further comprises a video signal input terminal 15, a common signal line 36, a vertical signal line 17, transfer switches 16 and 19 made up of MOS transistors, a gate line 18, a liquid crystal cell 20, a capacitor 21 for holding the charge, and a liquid crystal counter electrode (common electrode) 22.
Input video signals are sequentially selected by the horizontal shift register (HSR) 9 and transferred to the vertical signal lines 17 via the transfer switches 16. At this time, the vertical shift register (VSR) 12 selects a given gate line 18. Accordingly, a transfer switch 19 of a specific pixel selected as a matrix by the horizontal shift register (HSR) 9 and the vertical shift register (VSR) 12 is selected. The liquid crystal cell 20 and capacitor 21 are charged with the potential of the video signal of the specific pixel with respect to the potential of the counter electrode 22, thereby performing pixel display.
Along with the development of recent device technology, the number of pixels and the number of gradation levels in image display devices such as the liquid crystal panel greatly increase, and the data amount processed in the image display apparatus also increases. For example, the data amount is 5.5 Mbits/frame in VGA class (640xc3x97480 pixels and three R, G, B colors of 6-bit precision), 18.9 Mbits/frame in XGA class (1,024xc3x97768xc3x978 bitsxc3x97three colors), and 31.5 Mbits/frame in SXGA class (1,280xc3x971,024xc3x978 bitsxc3x97three colors). As the resolution and the number of gradation levels increase, the cost of the memory occupies a large proportion of the total cost.
However, the frame memory of a conventional image display apparatus, which has an amount necessary for the resolution of the image display unit, is mounted on the same board as the image processing unit. When an upgraded product having a larger number of display pixels is to be manufactured, a board 26 (dotted region in FIG. 13) for mounting a memory in size corresponding to the resolution of a new image display unit must be redesigned. The design load and uncommon components increase the cost.
Also, the board cannot be commonly used between a single-function product having only a frame memory, and an advanced-function product having a picture-in-picture function, a frame dividing function, and the like using many memories.
It is an object of the present invention to realize the lineup of a plurality of grades of products at a low cost by sharing the region except for the memory which occupies a large proportion of the total cost and by attaining a memory expandable arrangement in increasing the resolution and the number of functions in the display.
To achieve the above object, according to the present invention, there is provided an image display apparatus having image processing means for processing a digital signal, data memory means for storing data corresponding to at least one frame of an image, and image display means for displaying the image on the basis of an image signal from the image processing means, wherein the data memory means can be dismounted.
According to the present invention, there is provided an image display apparatus having image processing means for processing a digital signal, data memory means for storing data corresponding to at least one frame of an image, and image display means based on an image signal from the image processing means, wherein at least part of the data memory means can be added/removed.
According to the present invention, a non-data-memory means such as the image processing unit other than the data memory means can be shared by a plurality of products having different resolutions, different numbers of gradation levels, or different functions in the image display means. The development cost of the product can be reduced to easily realize cost reduction. The memory is divided in correspondence with divisional driving unique to the image display means, and part of the memory is dismounted or added/removed to simplify the system arrangement.
The present invention is applicable to any image display apparatus involving digital image processing such as a transmission or reflecting display, liquid crystal display, or display using FED (Field Emission Device) or SCE (Surface Conductive Emission Device), or PDP (Plasma Display Panel).